Screening And Structures Characterization Of Antioxidants From Some Extracts Of Herb

The herbs are valuable food and medicinal resources in China for many chemicalcomponets in such herbs have a strong antioxidant activity and can be used as naturalantioxidants. The effects of these natural antioxidants can be summarized as follows:reduce the oxidation reaction caused by free radicals, the effective prevention andtreatment of diseases, and anti-aging. The natural antioxidants were safer than artificalsynthetic antioxidant drugs. However, it is very hard to isolation and identificationpotential antioxidants from the extracts of herb with complicated systems by traditionalmethods. The drawbacks of the existing methodology caused not only unable tocompletely clarity the material basis and mechanism of active ingredients in herbs butalso limits the quality control of herbs and related products for entering theinternational market. So the development of rapid screening, identification, andevaluation methodology for herbs is very necessary. The main content in this thesis isas follows:(1) Establish the method can be used for screening, identification, and evaluationantioxifants from herbs by HPLC-ESI-MSHerein, a new method based on HPLC-MS for the rapid screening andidentification of antioxidants from herbs extract has been developed. An appropriateamount of diphenyl-1-picrylhydrazyl (DPPH·) was added to the herbs extract andincubated in dark place at room temperature for half an hour while DPPH· was replacedby methanol in the control group. This two group samples were analyzed byHPLC-ESI-MS. Comparing the chromatograms of experiment and control group, thepeak areas of antioxidants after the interaction with DPPH· had a decrease in thechromatogram while for those not responsible for DPPH· had no change in their peakareas. The relative binding affinities of antioxidants were calculated based on HPLC data while the structure identification was carried out based on MS data. This methodwhich was token the vantage of the enrichment function of liquid phase separationcould reduce the loss of trace componets during the process of extraction and separation.This method can also provide a theoretical and practical help to the system developed ofnatural antioxidant componets from herbs.(2) Screening and identification the potential antioxidants from serval herbs bythe established methoda. The established method was used for the methanol exacts of Scutellariae Radix.Four antioxidants were screen out from methanol extract of Scutellariae Radix by thisnovel method and were identified as baicalin, oroxylin A-7-O-glucuronide,wogonoside and oroxylin A based on HPLC and MS date. The activity order isoroxylin A> oroxylin A-7-O-glucuronide> wogonoside> baicalin.b. The established method was used for the methanol exacts of Psoraleacorylifolia L. Eight antioxidants were screen out from methanol extract of Psoraleacorylifolia L by this novel method and were identified as neobavaisoflavone, bavachin,corylin, psoralidin, isobavachalcone, bavachinin, corylifol, and bakuchiol based onHPLC and MS date. The activity order is bakuchiol> isobavachalcone> corylifol>corylin> neobavaisoflavone> bavachinin> psoralidin> bavachin.c: The established method was used for the methanol exacts of Stephaniatetrandra S. Moore. Four antioxidants were screen out from methanol extract ofStephania tetrandra S. Moore by this novel method and were identified asmagnocurarine, cyclanoline, fangchinoline, and tetrandrine based on HPLC and MSdate. The activity order is magnocurarine> fangchinoline> tetrandrine> cyclanoline.